I supply my Google Apps credentials each time I wipe off (hard reset) the phone. Though optional, I wipe off the phone’s data whenever I update my phone with a new ROM. Following the official and non official upgrades, I’m currently running CyanogenMod 4.2.14.1 on my ADP1.

Then came a day when I did not want to wipe off the data but only wanted to change the Google Account associated with the phone.This was the day when I wanted to play with Google Buzz which requires a GMail or non Google Apps account. I googled around and found solutions suggesting:

• Clear data for Gmail and Gmail storage under Manage Applications
• Clear data for Google Apps and you will see a message in the Android’s notification bar to setup a new Google account.

None of these worked for me. What worked for me is as follows:

• Goto Home (by clicking on the Home hardware button).
• Click on Menu (hardware button)
• Click/touch on Settings>Applications>Manage Applications.
• Click on Google Apps.
• Click on the button labelled “Clear data”
• When prompted with “All information you’ve saved in this application will be deleted permanently”, click on OK
• Subsequently, click on back button thrice and then click on “Data synchronization”. Alternatively, click on Home>Menu>Settings>Data synchronizaion.
• This will start the wizard which will prompt for a new Google account. This wizard is the same that you would have seen when you first (after you bought it) powered on the phone or whenever you wipe off the phone’s data.

This is what helped me in testing out Google Buzz on Google Maps on my Android phone. In your case, this may simply help you in changing the Google Account without hard resetting your Android.

Update (February 14, 2009): After following the above procedure, I noticed that though my E-mails were syncing, I could not search my E-mails. Whenever I typed in a search keyword in the GMail app and clicked on the search button, I saw a message saying something as “E-mails will sync shortly”. This can be fixed as follows. Goto Settings>Applications>Manage Applications>Gmail. Click on “Clear data” button.